1. Technical Field of the Invention
The present invention relates generally to a ceramic piezoelectric transformer, and more particularly to a ceramic piezoelectric transformer whose matching impedance is low and whose mechanical properties are improved so that a higher voltage may be output.
2. Background Art
Japanese Patent First Publication No. 11-8420 discloses a conventional ceramic piezoelectric transformer. The piezoelectric transformer includes voltage input and output portions. The voltage input portion is responsive to application of voltage to oscillate in an axial direction (i.e., a lengthwise direction) of the transformer, thereby inducing the resonance of the whole of the transformer. The voltage output portion serves to output the voltage and current produced by the resonance.
The above piezoelectric transformer, however, has a drawback that a sufficient voltage is not created. This is for the following reasons.
The output voltage and current of the ceramic piezoelectric transformer depend upon the geometry of the voltage output portion. Specifically, the creation of a higher voltage requires increasing the length of each ceramic piezoelectric element of the voltage output portion. Conversely, decreasing the matching impedance requires shortening each ceramic piezoelectric element of the voltage output portion. It is, thus, difficult to realize ceramic piezoelectric transformers which have a lower matching impedance, but is capable of producing a higher voltage.
Further, creating much voltage requires an increase in size of the transformer.
It is therefore a principal object of the present invention to avoid the disadvantages of the prior art.
It is another object of the present invention to provide a ceramic piezoelectric transformer whose matching impedance is low and which is capable of creating higher electric energy (e.g., higher voltage) without need of increase in size of the transformer.
According to one aspect of the invention, there is provided a ceramic piezoelectric transformer. The piezoelectric transformer comprises: (a) an input portion responsive to input of given energy to cause the piezoelectric transformer to resonate in a lengthwise direction of the piezoelectric transformer; (b) an output portion connected in alignment with the input portion, the output portion being responsive to resonance of the piezoelectric transformer to output energy in a given form; and (c) a compression mechanism adding a compressive stress to the input and output portions in a lengthwise direction thereof.
In the preferred mode of the invention, the compression mechanism includes a bolt and a nut. The bolt is inserted from an outer end of one of the input and output portions into a hole extending through lengths of the input and output portions. The nut is mounted on an outer end of the other of the input and output portions to fasten the bolt to subject the input and output portions to the compressive stress of a given level.
A weight block may be mounted on an end of one of the input and output portions for increasing the range of the output energy.
According to another aspect of the invention, there is provided a ceramic piezoelectric transformer. The transformer comprises: (a) an input portion responsive to input of given energy to cause the piezoelectric transformer to resonate in a lengthwise direction of the piezoelectric transformer; (b) an output portion connected in alignment with the input portion, the output portion being responsive to resonance of the piezoelectric transformer to output energy in a given form; and (c) a weight block mounted on an end of at least one of the input and output portions.
In the preferred mode of the invention, a compression mechanism may also be provided which adds a compressive stress to the input and output portions in a lengthwise direction thereof to absorb a tensile stress arising from the resonance of the transformer during operation for increasing the output energy.